The present invention relates to spacer fluids for use in subterranean operations and, more particularly, in certain embodiments, to foamed spacer fluids comprising cement kiln dust (“CKD”) and methods of use in subterranean formations.
Spacer fluids are often used in subterranean operations to facilitate improved displacement efficiency when introducing new fluids into a well bore. For example, a spacer fluid can be used to displace a fluid in a well bore before introduction of another fluid. When used for drilling fluid displacement, spacer fluids can enhance solids removal as well as separate the drilling fluid from a physically incompatible fluid. For instance, in primary cementing operations, the spacer fluid may be placed into the well bore to separate the cement composition from the drilling fluid. Spacer fluids may also be placed between different drilling fluids during drilling change outs or between a drilling fluid and a completion brine, for example.
To be effective, the spacer fluid can have certain characteristics. For example, the spacer fluid may be compatible with the drilling fluid and the cement composition. This compatibility may also be present at downhole temperatures and pressures. In some instances, it is also desirable for the spacer fluid to leave surfaces in the well bore water wet, thus facilitating bonding with the cement composition. Rheology of the spacer fluid can also be important. A number of different rheological properties may be important in the design of a spacer fluid, including yield point, plastic viscosity, gel strength, and shear stress, among others. While rheology can be important in spacer fluid design, conventional spacer fluids may not have the desired rheology at downhole temperatures. For instance, conventional spacer fluids may experience undesired thermal thinning at elevated temperatures. As a result, conventional spacer fluids may not provide the desired displacement in some instances.